Investigation of a COVID-19 outbreak in Germany resulting from a single travel-associated primary case: a case series

Abstract

Background In December, 2019, the newly identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, causing COVID-19, a respiratory disease presenting with fever, cough, and often pneumonia. WHO has set the strategic objective to interrupt spread of SARS-CoV-2 worldwide. An outbreak in Bavaria, Germany, starting at the end of January, 2020, provided the opportunity to study transmission events, incubation period, and secondary attack rates.Methods A case was defined as a person with SARS-CoV-2 infection confirmed by RT-PCR. Case interviews were done to describe timing of onset and nature of symptoms and to identify and classify contacts as high risk (had cumulative face-to-face contact with a confirmed case for ≥15 min, direct contact with secretions or body fluids of a patient with confirmed COVID-19, or, in the case of health-care workers, had worked within 2 m of a patient with confirmed COVID-19 without personal protective equipment) or low risk (all other contacts). High-risk contacts were ordered to stay at home in quarantine for 14 days and were actively followed up and monitored for symptoms, and low-risk contacts were tested upon self-reporting of symptoms. We defined fever and cough as specific symptoms, and defined a prodromal phase as the presence of non-specific symptoms for at least 1 day before the onset of specific symptoms. Whole genome sequencing was used to confirm epidemiological links and clarify transmission events where contact histories were ambiguous; integration with epidemiological data enabled precise reconstruction of exposure events and incubation periods. Secondary attack rates were calculated as the number of cases divided by the number of contacts, using Fisher's exact test for the 95% CIs.Findings Patient 0 was a Chinese resident who visited Germany for professional reasons. 16 subsequent cases, often with mild and non-specific symptoms, emerged in four transmission generations. Signature mutations in the viral genome occurred upon foundation of generation 2, as well as in one case pertaining to generation 4. The median incubation period was 4•0 days (IQR 2•3-4•3) and the median serial interval was 4•0 days (3•0-5•0). Transmission events were likely to have occurred presymptomatically for one case (possibly five more), at the day of symptom onset for four cases (possibly five more), and the remainder after the day of symptom onset or unknown. One or two cases resulted from contact with a case during the prodromal phase. Secondary attack rates were 75•0% (95% CI 19•0-99•0; three of four people) among members of a household cluster in common isolation, 10•0% (1•2-32•0; two of 20) among household contacts only together until isolation of the patient, and 5•1% (2•6-8•9; 11 of 217) among non-household, high-risk contacts.Interpretation Although patients in our study presented with predominately mild, non-specific symptoms, infectiousness before or on the day of symptom onset was substantial. Additionally, the incubation period was often very short ...

Comprehensive investigation of an in-hospital transmission cluster of a symptomatic SARS-CoV-2–positive physician among patients and healthcare workers in Germany

“…9 A low percentage of transmission to high-risk contacts (5%) has been reported in nonhousehold members. 10 Another study in the United States investigated the high-risk contacts of a patient among healthcare personnel (n = 32) and did not find any transmission, confirming our results. However, testing was only done in symptomatic persons after clinical monitoring, and asymptomatic transmission could have been missed.…”

COVID‐19: test, trace and isolate‐new epidemiological data

“…The serum antibodies cross-reacted with seasonal cold coronaviruses. Viral RNA, but not infectious virus, was detected after seroconversion and clinical recovery of the patients (Böhmer et al, 2020;Wölfel et al, 2020).…”

Overcoming Limitations in the Availability of Swabs Systems Used for SARS-CoV-2 Laboratory Diagnostics

“…In this setting, it may be required to test several times to con rm or rule out an infection of the test subject. This approach is considered a public health measure, because it detects SARS-CoV-2 infection early in pre-symptomatic subjects and enables the breach of infection chains 13,34,35 . Second, asymptomatic health-care workers and other staff working in hospitals or nursing homes, who are in contact with vulnerable groups of patients, can be screened for the safety of both co-workers and patients 36,37 .…”

“…Some RT-PCR tests are developed in-house, often following recommendations of reference laboratories and o cial institutions [10][11][12] . Other tests are commercially available and are in research use only (RUO) status or certi ed as invitro diagnostics (IVD) [13][14][15][16] . Typically, RTPCR tests are run in multiplex to detect two viral genes and one internal control in the same reaction well, tube or cartridge.…”